Transmission measuring system



Aug. '4, 1931. A. B. CLARK ET AL TRANSMISSION MEASURING SYSTEM Original Filed April '5. 1927 s 2 2 a E a s a 5 & R; &' R? N INVENTORS ilark fl mfiw ATTORNEY mission equivalent-o '5 of frequencles.

v A Patented Aug. 4, 1931 V UNITED. STATES PATENT OFFICE ALVA B. CLARK, OI WYOMING, AND FRED H. BEST, OF WES'IFIELD, NEW JERSEY, AS-

I SIGNORB TO AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A "CORPORATION O! NEW YORK TRANSMISSION MEASURING SYTEM Original application iiledlprll 5, 1927, Serial ll'o. 181,244, Iatent No. 1,748,241, dated I'ebrnary 11, 1930. Divided and this application filed August 23, 1928. Serial No. 387,984.

' 1 This invention relates to transmission measuring systems and particularly to means for readily indicatin or recording the transf a circuit at a plurality .This is a division of the copending application of Clark and Best, Serial No. 181,244, I filed .April -5, 1927, that issued as Patent 1,746,241, Feb. 11, 1930, and isintended to specifically cover Figure 2 of the said patent. Various systems have been proposed and used heretofore to determine the transmission equivalent of a circuit. Such systems have been designed to give very accurate results and require skillin their operation.

The object of this invention is to provide a system that will indicate or record the transmission equivalent of a circuit at various frequencies, the said system being characterlzed by greater simplicity of operation than the devices of the prior art.

Other objects of this invention will be apparent from the following description when read in connection'with the attached drawing which shows a form of the invention characterized by the simultaneous application of a plurality of frequencies. In the arrangement shown in the drawing, a plurality of oscillators, of which five designated 20 to 24, have been shown for the purpose of illustrating the invention, are connected across the primary winding of the transformer T The seconda 'is connected with the sending network R -H, which simulates the impedance of the line with which it is connected. At the opposite end of the line'L a plurality of condensers areconnected or adapted to be connected with the primary of the transformer T for the purpose of tuning it to a articular frequency the method of doing which will be described hereinafter. The circuit'is connected by the transformer T with an amplifier and rectifier 4, the output side of which is connected with a meter 6. This meter is calibrated to read directly the transmission equivalent of the L1. r The manner in which this arrangement is o erated to determine the transmission equiv a cut of the circuit L is as follows: By means other condensers will tune the transformer to line for the purpose of tun ng the trans.-

former to a particular frequency; thus when 25 is connected the transformer will be tuned to say 200 cycles. In like manner each of the one of the other frequencies transmitted. Fine adjustment of tuning is obtained by varying the condenser 30. This small condenser avoids the necessit of adjusting to a high degree of accuracy t e condensers con- 05 nected with the dial switch. When the trans: former has been tuned to resonance, it will be indicated by the position of the needle of the meter 6 which should stand at its maximum when resonance exists. The reading given by the meter 6 indicates the transmission equivalent of the circuit L, at that frequenc In like manner the equivalents for each requency throughout the range of frequencies produced by the oscillators 20 to 24 inclusive, may be obtained.

While the invention has been disclosed as embodied in a particular form, it is'of course obvious that the. underlying principle may assume other forms without departing from the spirit and scope of the appended claims.

What is claimed is:

1. In a transmission measuring system, the combination with a circuit whose transmission equivalent is to be measured, of a 85 source of electrical oscillations connected with the said circuit, the said source being ca able of impressing upon the said circult a plurality of discrete frequen- Y impressin a plurality of discrete fre uencies produced by the other sources, means connected with the said circuit to tune it for each of said frequencies, and means also connected with the said circuit to indicate the transmission equivalent thereof at each frequenc transmitted.

3. n a transmission measuring s stem, the combination with a circuit capa le of having its tuning. changed atwill, of a source of a plurality. of discrete frequencies lying within the band of frequencies for which the said circuit may be tuned, and an indicating device also connected with the said circuit to show the transmission equivalent thereof at each of the frequencies transmitted thereover. f

4. In a transmlssion measurlng. system, the combination with a circuit, whose transmission equivalent is to be measured, of a source of electrical oscillations connected therewith, the said source being capable of upon sai clrcuit, a group of con ensers, means to selectively connect each of" said condensers to said circuit to tune it for one of the frequencies produced by said source, andmeans also connected with said circuit to indicate the transmission equivalent of the circuit at the frequency transmitted thereover at any instant.

5. In a transmission measuring system, the combination with a circuit, whose transmission equivalent is to be measured, of a source of electrical oscillations connected therewith, the said source being ca able of impressing a plurality of discrete requencies upon said circuit, a group of,condensers, means to selectively connect each of said condensers to said circuit to tune it for one of the frequencies produced by said source, means connected with said circuit to amplify and rectify said oscillations, and a direct current responsive device connected with said rectifier to indicate the transmission equivalent of the circuit at the frequency transmitted at any instant.

In testimony whereof, we have si ed our names to this specification this 22n day of August, 1929.

ALVA B. CLARK. FRED H. BEST. 

